Mast cells play a pivotal role in the pathogenesis of asthma and other allergic diseases. These reactions are generally initiated by antigen-dependent aggregation of the high affinity IgE receptor (Fc-epsilon-RI) expressed on the cell surface and subsequent release of pro-inflammatory mediators (e.g. histamine, prostanoids, proteases and cytokines). However, ligands for other receptors such as KIT and various GPCRs may serve to prime mast cells for, or act as co-activators of, antigen-mediated mast cell activation. The signaling pathways linking Fc-epsilon-RI aggregation to human mast cell activation and function and how other receptors modify these Fc-mediated signaling events is unclear. Thus the primary focus of the research is the elucidation of signaling mechanisms associated with the activation of mast cells via the Fc-epsilon-RI and especially how the signaling pathways initiated by other receptors may integrate with those initiated by the Fc-epsilon-RI for synergistic mast cell activation and/or inhibition.